Certain harvesting machines have one or more drums open at the bottom which are driven so as to rotate about a substantially upright axis. Each of these drums is fitted at its base with a skirt in the form of substantially the shape of a hollow truncated cone.
When a machine of this type is operating, namely, when its drums are being rotated, their skirt, or skirts which is, or are continuously and constantly in contact with the ground, at least at the front of the machine as defined by the forward direction of its movement, pass or passes below the hay on the ground and lift the hay. Depending on the way in which the drums are disposed, it is possible, for example, either to lay hay in swaths, or to ted it.
Machines of this type have the advantage of being devoid of any metal prongs. As a result these machines do not constitute any danger for pick-up balers, forage harvesters or self-loading forage wagons, or the like, for there is no risk of a fragment of a metal prong passing into the hay-processing mechanisms of these machines. Similarly, there is no danger of the livestock swallowing any metal debris arising from a broken prong. Furthermore, the fact that the hay is tedded or laid on swaths by means of a skirt made of a flexible material makes it possible to treat the hay more gently than if it were tedded or laid in swaths with the aid of metal prongs. The hay is then handled less roughly, making it possible to harvest hay of a better nutritive quality. Finally, tedding or laying lay in swaths by means of skirts is less harmful to fresh growth than are metal prongs, favoring the growth of grass or vegetable matter for the following harvest.
However, the harvesting machines described above have the disadvantage that their skirts are relatively expensive. Furthermore, these skirts have parts which wear and have to be replaced several times during the life of the machine.
In fact, while the machines to which they are fitted are operative, the skirts are continuously and constantly in contact with the ground, at least at the front of the machine, as defined by the forward direction of the movement. The drums to which the skirts are attached, are driven so as to rotate, and therefore the skirts constantly rub the ground. This results in a process of wear, which can be minimized by a judicious choice of the material used to make the skirts. However, special materials for the skirts are very costly. Moreover, the skirts are of substantial dimensions, and their replacement is exceptionally expensive; also, some parts of the skirts, in spite of the quality of their material, may still have to be replaced.